> It looks as though you might have been trying to create the foreign
> key whilst the parent constraint was uncommitted.

I was able to create a separate fk from a different table. Also, in
trying to fix it using IBExpert, I disconnected and then reconnected
to the database and then tried to create the FK and the problem continued.

The Primary key exists on the source table, I just can't create the FK
from one detail table.

Any other things I may look at?